Abstract:We present the first frequency-dependent analyses of the
geographic smoothing of wind power's variability, analyzing the
interconnected measured output of 20 wind plants in Texas. Reductions in
variability occur at frequencies corresponding to times shorter than ~24
hours and are quantified by measuring the departure from a Kolmogorov
spectrum. At a frequency of 2.8x10-4 Hz (corresponding to 1 hour), an 87%
reduction of the variability of a single wind plant is obtained by
interconnecting 4 wind plants. Interconnecting the remaining 16 wind plants
produces only an additional 8% reduction. At a frequency of 4.6x10-5 Hz (6
hours), interconnecting 6 wind plants produces a 68% reduction in
variability and interconnecting the remaining 14 wind plants produces only
an additional 8% reduction. We use step-change analyses and correlation
coefficients to compare our results with previous studies, finding that wind
power ramps up faster than it ramps down for each of the step change
intervals analyzed and that correlation between the power output of wind
plants 200 km away is half that of co-located wind plants. To examine
variability at very low frequencies, we estimate yearly wind energy
production in the Great Plains region of the United States from automated
wind observations at airports covering 36 years. The estimated wind power
has significant inter-annual variability and the severity of wind drought
years is estimated to be about half that observed nationally for
hydroelectric power.

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